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. Author manuscript; available in PMC: 2017 Oct 4.
Published in final edited form as: Biochemistry. 2016 Sep 19;55(39):5595–5609. doi: 10.1021/acs.biochem.6b00645

Figure 4.

Figure 4

Autophosphorylation kinetics of wild type CheY and position T+1 mutants using PAM as the phosphodonor. (A) Wild type CheY (closed squares), the polar mutants CheYA88S (open circles) and CheYA88T (open squares), as well as CheYA88M (closed circles). (B) β-branched mutants CheYA88V (closed triangles) and CheYA88I (open triangles). Note the difference in y-axis scales between panels A and B. Rate constants were determined by stopped-flow fluorescence at constant ionic strength. kobs is the observed rate constant for the approach to equilibrium between autophosphorylation and autodephosphorylation: kobs = (kphos/Ks)[phosphodonor] + kdephos 9, 34. Hence, the slope of the best-fit lines is the effective autophosphorylation rate constant kphos/Ks and the y-intercept is the autodephosphorylation rate constant kdephos. Note the close agreement (after conversion from units of s−1 to min−1) between kdephos values determined here and those measured by pH jump experiments (Table 2).